From b5164cf836d28b83f9123ec04c0e4189e0da1723 Mon Sep 17 00:00:00 2001
From: Zhanglong Xia <zhanglongxia@google.com>
Date: Thu, 27 Feb 2025 11:53:37 +0800
Subject: [PATCH] [posix] remove the polling mode from spi interface (#11303)

The RCP should assert the interrupt pin to notify the SPI interface of
an impending data frame transfer to the host. This commit removes the
polling mode from the spi interface.
---
 src/posix/platform/radio_url.cpp     |  5 +--
 src/posix/platform/spi_interface.cpp | 57 +++++++++-------------------
 src/posix/platform/spi_interface.hpp |  1 -
 3 files changed, 19 insertions(+), 44 deletions(-)

diff --git a/src/posix/platform/radio_url.cpp b/src/posix/platform/radio_url.cpp
index b49bed6e2..e89a90d4e 100644
--- a/src/posix/platform/radio_url.cpp
+++ b/src/posix/platform/radio_url.cpp
@@ -49,12 +49,9 @@ const char *otSysGetRadioUrlHelpString(void)
     "Parameters:\n"                                                                                            \
     "    gpio-int-device[=gpio-device-path]\n"                                                                 \
     "                                  Specify a path to the Linux sysfs-exported GPIO device for the\n"       \
-    "                                  `I̅N̅T̅` pin. If not specified, `SPI` interface will fall back to\n" \
-    "                                  polling, which is inefficient.\n"                                       \
+    "                                  `I̅N̅T̅` pin.\n"                                                     \
     "    gpio-int-line[=line-offset]\n"                                                                        \
     "                                  The offset index of `I̅N̅T̅` pin for the associated GPIO device.\n"  \
-    "                                  If not specified, `SPI` interface will fall back to polling,\n"         \
-    "                                  which is inefficient.\n"                                                \
     "    gpio-reset-dev[=gpio-device-path]\n"                                                                  \
     "                                  Specify a path to the Linux sysfs-exported GPIO device for the\n"       \
     "                                  `R̅E̅S̅` pin.\n"                                                     \
diff --git a/src/posix/platform/spi_interface.cpp b/src/posix/platform/spi_interface.cpp
index 4c196f195..57fd11983 100644
--- a/src/posix/platform/spi_interface.cpp
+++ b/src/posix/platform/spi_interface.cpp
@@ -150,16 +150,7 @@ otError SpiInterface::Init(ReceiveFrameCallback aCallback, void *aCallbackContex
     mSpiSmallPacketSize = spiSmallPacketSize;
     mSpiAlignAllowance  = spiAlignAllowance;
 
-    if (spiGpioIntDevice != nullptr)
-    {
-        // If the interrupt pin is not set, SPI interface will use polling mode.
-        InitIntPin(spiGpioIntDevice, spiGpioIntLine);
-    }
-    else
-    {
-        LogNote("SPI interface enters polling mode.");
-    }
-
+    InitIntPin(spiGpioIntDevice, spiGpioIntLine);
     InitResetPin(spiGpioResetDevice, spiGpioResetLine);
     InitSpiDev(mRadioUrl.GetPath(), spiMode, spiSpeed);
 
@@ -606,16 +597,12 @@ exit:
     return error;
 }
 
-bool SpiInterface::CheckInterrupt(void)
-{
-    return (mIntGpioValueFd >= 0) ? (GetGpioValue(mIntGpioValueFd) == kGpioIntAssertState) : true;
-}
+bool SpiInterface::CheckInterrupt(void) { return (GetGpioValue(mIntGpioValueFd) == kGpioIntAssertState); }
 
 void SpiInterface::UpdateFdSet(void *aMainloopContext)
 {
-    struct timeval        timeout        = {kSecPerDay, 0};
-    struct timeval        pollingTimeout = {0, kSpiPollPeriodUs};
-    otSysMainloopContext *context        = reinterpret_cast<otSysMainloopContext *>(aMainloopContext);
+    struct timeval        timeout = {kSecPerDay, 0};
+    otSysMainloopContext *context = reinterpret_cast<otSysMainloopContext *>(aMainloopContext);
 
     assert(context != nullptr);
 
@@ -626,31 +613,23 @@ void SpiInterface::UpdateFdSet(void *aMainloopContext)
         timeout.tv_usec = 0;
     }
 
-    if (mIntGpioValueFd >= 0)
+    if (context->mMaxFd < mIntGpioValueFd)
     {
-        if (context->mMaxFd < mIntGpioValueFd)
-        {
-            context->mMaxFd = mIntGpioValueFd;
-        }
-
-        if (CheckInterrupt())
-        {
-            // Interrupt pin is asserted, set the timeout to be 0.
-            timeout.tv_sec  = 0;
-            timeout.tv_usec = 0;
-            LogDebg("UpdateFdSet(): Interrupt.");
-        }
-        else
-        {
-            // The interrupt pin was not asserted, so we wait for the interrupt pin to be asserted by adding it to the
-            // read set.
-            FD_SET(mIntGpioValueFd, &context->mReadFdSet);
-        }
+        context->mMaxFd = mIntGpioValueFd;
     }
-    else if (timercmp(&pollingTimeout, &timeout, <))
+
+    if (CheckInterrupt())
     {
-        // In this case we don't have an interrupt, so we revert to SPI polling.
-        timeout = pollingTimeout;
+        // Interrupt pin is asserted, set the timeout to be 0.
+        timeout.tv_sec  = 0;
+        timeout.tv_usec = 0;
+        LogDebg("UpdateFdSet(): Interrupt.");
+    }
+    else
+    {
+        // The interrupt pin was not asserted, so we wait for the interrupt pin to be asserted by adding it to the
+        // read set.
+        FD_SET(mIntGpioValueFd, &context->mReadFdSet);
     }
 
     if (mSpiTxRefusedCount)
diff --git a/src/posix/platform/spi_interface.hpp b/src/posix/platform/spi_interface.hpp
index 43d311cb8..5524b5b01 100644
--- a/src/posix/platform/spi_interface.hpp
+++ b/src/posix/platform/spi_interface.hpp
@@ -201,7 +201,6 @@ private:
     {
         kMsecPerSec              = 1000,
         kUsecPerMsec             = 1000,
-        kSpiPollPeriodUs         = kMsecPerSec * kUsecPerMsec / 30,
         kSecPerDay               = 60 * 60 * 24,
         kResetHoldOnUsec         = 10 * kUsecPerMsec,
         kImmediateRetryTimeoutUs = 1 * kUsecPerMsec,